Field of the Invention
The invention relates to a knob structure, and more particularly to a knob structure in which bulge portions continuously engage with and disengage from depressed portions in a relative rotation so that the user can feel clicks.
Description of the Related Art
Referring to FIG. 1, a known knob 10 for adjusting the brightness of a sight includes a base 2, a rotational element 4 and a clicking sheet 6. The base 2 is fixed to a sight (not shown). The rotational element 4 is rotatably mounted on the base 2. The clicking sheet 6 is disposed in the rotational element 4. A circuit board 3 is disposed over the clicking sheet 6. The circuit board 3 and the clicking sheet 6 are fixed to the base 2 via a bolt 5. A plurality of contact pins 1 are mounted on the circuit board 3. Tips of the contact pins 1 contact pads of another circuit board 7. The circuit board 7 is disposed in the rotational element 4. A battery 8 is disposed on and electrically connected to the circuit board 7. A cap assembly 9 covers the rotational element 4 to position the battery 8 on the circuit board 7. When the rotational element 4 is rotated by an external force, the cap assembly 9, the battery 8 and the circuit board 7 follow the rotational element 4 to rotate with respect to the base 2 and the circuit board 7 is rotated with respect to the tips of the contact pins 1, thereby regulating the magnitude of the electric current and the brightness of the sight.
FIGS. 2A and 2B depict the rotational element 4, wherein the rotational element 4 has a plurality of inner protrusions 42 and openings 44 formed between the inner protrusions 42. FIGS. 3A and 3B depict the clicking sheet 6, wherein the clicking sheet 6 has two triangular bulge portions 62 on opposite sides. Referring to FIG. 1, the inner protrusions 42 of the rotational element 4 are disposed between the clicking sheet 6 and the base 2. The clicking sheet 6 is fixed to the base 2 through the bolt 5 so that the clicking sheet 6 is forced against the inner protrusions 42 of the rotational element 4, with the bulge portions 62 engaging with the openings 44. When the rotational element 4 is rotated, the inner protrusions 42 are rotated with respect to the clicking sheet 6 and the bulge portions 62 continuously engage with and disengage from the openings 44 so that the user can feel clicks.
Generally, the rotational element 4 is made of aluminum to meet the lightweight and anti-corrosion requirements. If the rotational element 4 is made of steel, then the manufacturing cost will be significantly increased. However, the clicking sheet 6 is made of steel which is harder than aluminum. Therefore, the openings 44 of the aluminum rotational element 4 are susceptible to wear caused by the triangular bulge portions 62 after a certain number of operations, the openings 44 become wider due to the wear, and the bulge portions 62 engaging with the openings 44 are loosened. As a result, the user fails to clearly feel the clicks and the accuracy of positioning of the knob is reduced. Further, the bulge portions 62 are triangular and the openings 44 are substantially rectangular. It is difficult to determine the interference between the bulge portions 62 and the openings 44 according to the theory of mechanics. Therefore, it is necessary to compensate and regulate the interference between the bulge portions 62 and the openings 44 according to the actual situation, which also increases the manufacturing cost.